JPS5821875B2 - How to play video signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The following methods can be considered as methods for recording color video signals on a magnetic tape or the like.

As shown in Figure 1E, this means that for the luminance signal,
The carrier frequency is extracted as a mainly upper side band amplitude modulated signal YD with a low carrier frequency, for example, fD21.18M, and the carrier color signal is extracted as an amplitude-modulated signal YD with a low carrier frequency of, for example, fD21.18M.
Modulated luminance signal Y such that L = 0.59 MHz
The signal CL is frequency-converted to be lower than the carrier frequency fD of D, and a composite signal of the modulated luminance signal and the low frequency-converted carrier color signal CL is recorded on a magnetic tape or the like.

According to this method, the S/N ratio can be improved, and the loss caused by the gap between the head gap and the recording medium, so-called spacing loss, can be reduced.

That is, the recording and reproducing characteristics of magnetic tape etc. peak at relatively low frequencies, for example around IMHz, but
In this method, since the carrier frequency of the modulated luminance signal is lowered, the carrier frequency comes to be around this peak, so that the S/N of the luminance signal is improved.

Furthermore, since the spacing loss increases as the signal frequency increases, the spacing loss can be reduced by lowering the carrier frequency of the luminance signal in this manner.

The present invention relates to a method for reproducing a recording medium on which a color video signal is recorded in such a manner, and in particular, it is a method that reliably obtains a stable and desired reproduced color video signal with a simple configuration. be.

Before explaining the method of the present invention, first, a specific method for recording as described above will be explained with reference to FIG.

In Fig. 2, reference numeral 1 denotes an input terminal for a color video signal, and the color video signal from this input terminal is supplied to a rotary filter 2 to generate a luminance signal Y of components up to fB2 and 2.99MHz.
(A in FIG. 1) is taken out and supplied to the balanced modulator 3, and on the other hand, when the horizontal frequency from the variable frequency oscillator 4 is fH, the relationship is fL2n+1 f (n is an appropriate positive 5 integer) ), for example, fL=one axis=0.59MHz signal,
A signal of f3=3.58MHz from the oscillator 5 is supplied to the frequency converter 6, and "l f B - f L - f B = 2
゜99MHz signal and f +f = f =4.17
■ Obtain the signal of h and use the filter to f B = 2.99
Take out the MHz signal and pass it through filter 8 to fC24-17
Take out the MHz signal and use f − from this filter.
A 2.99 MHz signal is supplied to the balanced modulator 3 and balanced modulated by the luminance signal "chi", from which the modulated luminance signal YB
(Figure 1B) is obtained.

In this case, for example, as shown in FIGS. 5A and 5B, the modulated luminance signal YB has an amplitude of a portion MH corresponding to the synchronization signal SN (of the luminance signal YA) that is larger than the amplitude of other portions, i.e. The width should be wider than the amplitude of the portion corresponding to the white level and black level of the signal YA.

And this modulated luminance signal Y is f = 2.99M
Specially reduced by 6dB at Hz.

BB is supplied to a vestigial sideband filter 9, mainly the lower sideband component Y.

(FIG. 1C) is taken out and supplied to the synthesizer 10'.

The input color video signal is also passed through a bandpass filter 1.
A carrier chrominance signal C8 (FIG. 1C) with a carrier frequency of f s =3.58 MHz is obtained by supplying it to a synthesizer 10 to generate a modulated luminance signal Y.

Synthesize with And the composite signal Y.

+C8 is supplied to the frequency converter 12, and the frequency is converted using the fc24.17 MHz signal from the filter 8, and the carrier frequency of the luminance signal is fD2f.

-fB=(f8+fL) -(f8-fL) =2 f
t, a mainly upper sideband signal Y9 of 2 1.18 MHz, and a carrier frequency fF, = fo + fB = 2fS
= 7.16 MHz predominantly lower sideband signal Y.

Also, for the carrier color signal, the carrier frequency is fL=f
cfS=fs=signal CL of 0.59MHz and carrier frequency is f2f+f=2 f8+fL=7.7
A signal q of 5C8 MHz is obtained (Fig. 1D).

Then, these signals YD, YD, CL, and V are supplied to a low-pass filter 13 so that the carrier frequency fD is equal to fD21.18.
MHz low mainly upper sideband modulated luminance signal YD
, the carrier frequency converted to the lower frequency side is fL
” The first to extract the carrier color signal cL of 0.59 MHz.
(Fig. E), this is passed through the recording amplifier 14 to the magnetic head 15.
and record it on, for example, a magnetic tape.

In this case, the input color video signal is supplied to the horizontal synchronization signal separation circuit 16 to extract a horizontal synchronization signal, which is supplied to the phase comparator circuit 17, and the fL knee axis from the variable frequency 5-frequency oscillator 4 -0.59 MHz. The signal is supplied to the frequency divider 18 and divided by - to produce a signal on the horizontal frequency axis, which is then supplied to the phase comparison circuit 17, and the comparison error voltage is supplied to the variable frequency oscillator 4 to generate its oscillation. The frequency is controlled, and the carrier color signal C8 from the bandpass filter 1 is supplied to the vanist gate circuit 19, and the horizontal synchronizing signal from the circuit 16 is supplied to the waveform shaping circuit 20 to obtain a burst gate signal. The burst signal is supplied to the burst gate circuit 19 to increase the burst signal, and the oscillator 5 is driven synchronously with the burst signal.

The present invention reproduces from a recording medium a composite signal of the above-mentioned modulated luminance signal Y9 having a low carrier frequency, mainly in the upper band, and a carrier color signal CL occupying the lower frequency side thereof, and reproduces these modulated luminance signals YD and CL. The carrier chrominance signal cL is frequency-converted, and the frequency-converted modulated luminance signal is synchronously detected. In particular, the above-mentioned frequency conversion signal and synchronous detection signal are converted into the same signal obtained from the reproduced signal. It is designed to be controlled by signals.

FIG. 3 shows an example of this, in which the reproduction signals Y9 and CL (E in FIG. 1) from the magnetic head 21 are supplied to the frequency converter 23 through the reproduction amplifier 22, while the f L" O− from the variable frequency oscillator 24 is supplied. The 59 MHz signal and the fs-3, 58 MHz signal from the oscillator 25 are supplied to the frequency converter 26 to obtain the f8-fL-fB22.99 MHz signal and the f8+fL=fo=4.17 MHz signal, and the filter A signal of fB = 2.99 MHz is taken out from the filter 27, a signal of fC24 and 17 MHz is taken out from the filter 28, and the f from this filter 28 is taken out.

A signal of =4.17MHz is supplied to the frequency converter 23 to convert the frequency of the reproduced signals YD and CL, and for the luminance signal, the carrier frequency is fB=fc fD22.99MH
The signal YF is mainly the lower sideband of z, and the carrier frequency is f
.

-=fc10fD2 5.35MHz mainly upper band signal Y.

, and for the carrier color signal, the carrier frequency is f8=
A signal c8 with fo-f L =3.58 MHz and a signal C□ with carrier frequency f, = fc + fL = 4.76 MHz are obtained (FIG. 1F).

These signals YF, YG) C3 and H C□ are supplied to a low-pass filter 29, and a signal Y is obtained from the filter 9 during recording.

Similar to (Fig. 1C), the carrier frequency is fB = 2.99M
The modulated luminance signal "G", which is mainly a lower side band wave in Hz, is extracted (Fig. 1G), and is supplied to the synchronous detection circuit 30, where it is synchronously detected using the f B = 2.99 MHz signal from the filter 27. , the detected luminance signals are supplied to the synthesizer 31, and the signals □, YG, CS, and C□ from the frequency converter 23 are supplied to the band pass filter 32, and the carrier frequency is f8 and 3.58 MHz. The color signal C8 is extracted (FIG. 1H) and is supplied to the synthesizer 31 where it is combined with the luminance signal to obtain a reproduced color image signal at the output terminal 33.

In this case, the modulated luminance signal YF from the filter 29 is
Similar to the modulated luminance signal YB obtained from the balanced modulator 3 during recording, as shown in FIG. 5B, the amplitude of the portion MH corresponding to the synchronization signal is larger than the amplitude of other portions. , this modulated luminance signal ■ is supplied to the gate circuit 34, and is also sent to the envelope detection circuit 351/i:
The detection output is supplied to the synchronization signal position detection circuit 36 to obtain a gate signal at the synchronization signal position, and this is supplied to the gate circuit 34, from which the frequency is fB22.99MH.
Extract the part MH corresponding to the synchronization signal of z (Figure 5C)
, is supplied to the phase comparison circuit 37 to compare the phase with the fB=2.991VH (z signal from the filter 27), and the comparison error voltage is supplied to the variable frequency oscillator 24 to control its oscillation frequency.

According to such a circuit configuration, the carrier frequency fD of the modulated luminance signal is now equal to the carrier frequency fL of the low-pass converted carrier chrominance signal.
Therefore, the amount of phase variation with respect to frequency fD due to the same / - time axis variation of the tape should be twice that with respect to frequency fL.

Therefore, the recovered carrier frequency fD including the amount of phase variation
and fL can be respectively expressed as follows.

fD+2Δψ fL+Δψ On the other hand, the oscillation frequency from the variable frequency oscillator 24 is subjected to feedback control to remove phase fluctuations from the signal from the frequency converter 26, so the oscillation frequency of the oscillator 24 is selected to be fL. If there is, the oscillation frequency from the oscillator 24 will be fL+Δψ.

This oscillation signal is added by a frequency converter 26 to a reference signal having a frequency f8 from the reference oscillator 25, and a converted signal having a frequency fC is obtained from a filter 28.

However, even if the frequency is converted from fL to f8+fL, the absolute magnitude of the phase variation remains Δψ because the frequency is converted from the reference signal.

Therefore, the conversion signal fC can be expressed as follows.

fo = f8 + fL + Δψ Therefore, the carrier color signal frequency-converted to the original frequency band by the frequency converter 23 is fo - (fL + Δψ) = (f8 + fL + Δψ) - (fL
+Δψ)=f8, so jitter is removed.

Also, regarding the modulated luminance signal, fC-(fD+2Δψ)=(fD+fB+Δψ)-(f
D+2Δψ)=fB−Δψ, and the jitter remains by Δψ.

However, the modulated luminance signal is further processed by the synchronous detection circuit 30.
Since it is detected by the synchronous detection signal from the filter 27, the remaining jitter Δψ is also removed.

That is, since the synchronous detection signal fB is expressed as f8-(fL+Δψ1=fB-Δψ), no jitter is added to the detection output.

Furthermore, as shown in FIG. 5A, depending on whether the original luminance signal YA is on the white level side or on the black level side with respect to the intermediate level between the white level and the black level shown by the straight line a, the figure If it is a sawtooth wave like , it is either section TA or section T
Even if the phase of the balanced modulated signal YB, and thus the modulated luminance signal YF obtained from the filter 20, is inverted, the fB of the filter 37 is 2.99
Since the MHz synchronous detection signal is synchronized with the phase of the partial signal corresponding to the synchronous signal, the detected luminance signal is the same as the signal l obtained from the filter 2 during recording. A brightness signal of

Therefore, the carrier color signal C from the filter 32 is outputted to the output end 33 as shown in the example of FIG.
8 to the burst gate circuit 38, and similarly to the above, the modulated luminance signal Y from the filter 29 is supplied to the envelope detection circuit 35, and its detection output is supplied to the synchronization signal position detection circuit 36 for synchronization. A gate signal is obtained at the signal position, this is further supplied to the delay circuit 39 to obtain a burst gate signal, this is supplied to the burst gate circuit 38, a burst signal is extracted from this, and this is sent to the phase comparator circuit 4.
0 to compare the phase with the f823.58 MHz signal from the oscillator 25, and the comparison error voltage may be supplied to the variable frequency oscillator 24 to control its oscillation frequency.

In recording, the luminance signal may be subjected to normal amplitude modulation without being balanced modulated.

Furthermore, the carrier frequency fD of the modulated luminance signal to be recorded on the recording medium may be selected to be three or four times the carrier frequency fL of the carrier color signal converted to the lower frequency side if it can be lower than the above-mentioned value. Also, it is not necessarily necessary to select an integer multiple of the carrier frequency fL of this carrier color signal, but it is necessary to select a low frequency within a range where the spectrum of the modulated luminance signal and the spectrum of the carrier color signal converted to the low frequency side do not overlap. It's good.

According to the method of the present invention described above, both the modulated luminance signal YD, which is mainly an upper band wave with a low carrier frequency, and the carrier color signal cL, which occupies the lower band side thereof, are frequency-converted, and the frequency-converted modulated luminance signal Since the signal is synchronously detected and the signals for frequency conversion and synchronous detection are controlled by the signal obtained from the reproduced signal, the jitter of each of the luminance signal and carrier chrominance signal can be eliminated. Both can be reliably removed.

Furthermore, since the signals for frequency conversion and signals for synchronous detection are controlled by the same signal obtained from the reproduced signal, the configuration is extremely simple.

[Brief explanation of drawings]

FIG. 1 is a spectrum diagram for explaining the invention, FIG. 2 is a system diagram of the recording method, and FIGS. 3 and 4 are system diagrams of an example of a device applied to the method of the present invention, respectively. FIG. 5 is a waveform diagram for explaining the present invention. 23 is a frequency converter, 29 is a low-pass filter, 30 is a synchronous detection circuit, and 32 is a band-pass filter.

Claims (1)

[Claims] 1. A first amplitude-modulated luminance signal mainly in the upper side band with a low carrier frequency, and a second amplitude-modulated luminance signal below the amplitude-modulated luminance signal.
When reproducing a recording medium on which a carrier color signal whose frequency has been converted to have a carrier frequency of and controlling the frequency of the carrier based on the oscillation signal from the variable frequency oscillator such that the frequency-converted carrier color signal has the original carrier frequency when the frequency is re-converted. forming a converted signal and a synchronous detection signal having a frequency equal to the frequency at which the first carrier frequency is reconverted when the frequency of the amplitude modulated luminance signal is reconverted, and reproducing the frequency reconverted. The amplitude modulated luminance signal is extracted from the lower side band of the signal and synchronously detected using the synchronous detection signal to obtain the original luminance signal, and the original carrier chrominance signal is directly extracted from the frequency reconverted reproduced signal. obtained,
A video signal reproduction method in which these luminance signals and carrier color signals are added.